/*
 * See the NOTICE file distributed with this work for additional
 * information regarding copyright ownership.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */
package com.yoshtec.owl.util;

import java.io.File;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.net.JarURLConnection;
import java.net.URL;
import java.net.URLDecoder;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Enumeration;
import java.util.List;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 *
 */
public final class ClassUtil {

	private final static Logger log = LoggerFactory.getLogger(ClassUtil.class);
	
	/**
	 * Collects all the currently avialable classes in a 
	 * package. E.g. all the classes that are in the class path.
	 * 
	 * Taken from the 
	 * <a href="http://forum.java.sun.com/thread.jspa?threadID=341935&start=15&tstart=0">
	 * Java Development Forums</a>
	 * 
	 * @author Thanos.Panousis
	 * 
	 * @param pckgname Java Package Name
	 * @return List of classes of the Package
	 * @throws ClassNotFoundException
	 */
	public static List<Class<?>> getClassesForPackage(String pckgname) 
	throws ClassNotFoundException {
		// This will hold a list of directories matching the pckgname. 
		// There may be more than one if a package is split over multiple jars/paths
		List<Class<?>> classes = new ArrayList<Class<?>>();
		ArrayList<File> directories = new ArrayList<File>();
		try {
			ClassLoader cld = Thread.currentThread().getContextClassLoader();
			if (cld == null) {
				throw new ClassNotFoundException("Can't get class loader.");
			}
			String pathpckgname = pckgname.replace('.', '/');
			// Ask for all resources for the path
			Enumeration<URL> resources = cld.getResources(pathpckgname);
			while (resources.hasMoreElements()) {
				URL res = resources.nextElement();
				if (res.getProtocol().equalsIgnoreCase("jar")){
					JarURLConnection conn = (JarURLConnection) res.openConnection();
					JarFile jar = conn.getJarFile();
					for (JarEntry e : Collections.list(jar.entries())){

						if (e.getName().startsWith(pathpckgname) 
								&& e.getName().endsWith(".class") && !e.getName().contains("$")){
							String className = 
								e.getName().replace("/",".").substring(0,e.getName().length() - 6);
							log.debug("Class Found {}", className);
							classes.add(Class.forName(className));
						}
					}
				}else
					directories.add(new File(URLDecoder.decode(res.getPath(), "UTF-8")));
			}
		} catch (NullPointerException x) {
			throw new ClassNotFoundException(pckgname + " does not appear to be " +
			"a valid package (Null pointer exception)");
		} catch (UnsupportedEncodingException encex) {
			throw new ClassNotFoundException(pckgname + " does not appear to be " +
			"a valid package (Unsupported encoding)");
		} catch (IOException ioex) {
			throw new ClassNotFoundException("IOException was thrown when trying " +
					"to get all resources for " + pckgname);
		}

		// For every directory identified capture all the .class files
		for (File directory : directories) {
			if (directory.exists()) {
				// Get the list of the files contained in the package
				String[] files = directory.list();
				for (String file : files) {
					// we are only interested in .class files
					if (file.endsWith(".class")) {
						// removes the .class extension
						classes.add(Class.forName(pckgname + '.' 
								+ file.substring(0, file.length() - 6)));
					}
				}
			} else {
				throw new ClassNotFoundException(pckgname + " (" + directory.getPath() + 
				") does not appear to be a valid package");
			}
		}
		return classes;
	}


	public static List<Class<?>> getClassessOfInterface(String thePackage, Class<?> theInterface) {     
		List<Class<?>> classList = new ArrayList<Class<?>>();
		try {
			for (Class<?> discovered : getClassesForPackage(thePackage)) {
				if (Arrays.asList(discovered.getInterfaces()).contains(theInterface)) {
					classList.add(discovered);
				}
			}
		} catch (ClassNotFoundException ex) {
			log.warn("Cannont find class",ex);
		}

		return classList;
	}


}
